I was hearing from some growers earlier this week, was called separately by another, and saw for myself when I was looking over the UVM orchard yesterday some concerning issues with fruit quality that I ascribe to a ‘hormone / stress mess’ in some situations. Many of us are seeing frost rings, the rusted bands around fruit caused by cell damage from the May 18 freeze event. In many cases, as those fruit size up, this damaged skin tissue won’t be able to expand and we can expect a fair amount of fruit splitting as a result. That’s not unexpected.
Of another level of concern are issues I am seeing with ripening and sizing fruit. I have been hearing talk of and have been seeing myself fruit that just doesn’t seem to be sizing well, especially given low crop load and more than ample moisture. Now, I am seeing increased preharvest fruit drop and weirdly uneven ripening. For example, we have Liberty fruit in the UVM orchard that are dropping prematurely while showing signs of over ripeness- deep red color, waxy skin, soft flesh- but are flavorless. This was on August 16, and we normally harvest out Liberty six weeks from now.
My hypothesis regarding what’s going on is that we are seeing the results of a hormonal confusion in trees and fruit this year. In spring, developing seeds in the blossom’s ovary excrete hormones that signal the tree to develop a fruit to protect them. Upon inspection of the fruit buds in the days following the freeze, any damage was assumed to result in lost fruit. However, many fruit did form, and some buds that may not have shown damage may have still sustained it. As we approach harvest, we are seeing that many fruit are showing poorly-developed seeds, tissue damage around the core, or even no seeds at all. I believe that this poor or damaged seed development is behind the paradoxical poor fruit sizing and preharvest fruit drop. I also expect this drop to continue as trees have since the freeze been subject to a number of other stressors, including air pollution from the Canadian wildfires and the unceasing rain.
This brings up the question about applying Retain to reduce apple drop and improve fruit quality this season. ReTain is a plant growth regulator that slows ethylene production in fruit and thus delays harvest and fruit drop. It should be applied 7-30 days prior to harvest, based on the need and maturity of the fruit. But the trees aren’t responding normally to anything this year. Furthermore, the ReTain label states to not apply to trees that are “nutrient, water, insect, or disease stressed.” And it’s expensive, in a year when many of us are needing to reduce costs in the orchard.
Here’s my advice- if you have a ‘normal’ to light crop, but enough fruit that you expect 200+ bushels per acre, then you might consider using ReTain. It won’t be worth saving a crop of straggler fruit that are hard to find, and it won’t stop a dropping crop from continuing to drop. And if trees are showing real signs of stress, especially in wet orchards, I wouldn’t expect much for the money you’ll be spending. As I said before, the normal suite of plant hormones that regulate fruiting seems to be out of whack this year, and another hormonal nudge, which is basically what you’re doing when you apply PGRs, may provide similarly unpredictable results.
Good luck out there,